Wiper blade

ABSTRACT

A wiper blade for a windshield wiper, in particular for a windshield wiper of a motor vehicle, is proposed, which has a wiper blade rubber with a wiper blade rubber lip ( 2 ). In order to achieve a low dry friction coefficient, the wiper blade rubber lip ( 2 ) is fabricated partially of polyethylene (FIG.  1 ).

STATE OF THE ART

[0001] The invention starts with a wiper blade for a windshield wiper, in particular for a windshield wiper of a motor vehicle, in accordance with the type defined in more detail in the pre-characterizing clause of Patent Claim 1 as well as a process to manufacture a wiper blade in accordance with the type defined in more detail in the pre-characterizing claim of Patent Claim 7.

[0002] A wiper blade of the type cited at the outset is known from practice and is comprised of a wiper blade rubber, which is embodied with a wiper blade rubber lip. The wiper blade rubber or the wiper blade rubber lip is composed of a rubber material, which is manufactured on the basis of natural rubber, for example.

[0003] Wiper blade rubbers or wiper blade rubber lips of known wiper blades have the disadvantage that they have relatively high dry friction coefficients μ_(tr) when they are applied to a glass of a conventional windshield.

[0004] These types of dry friction coefficients, which lie between 0.8 and 1.2 and are higher than the friction coefficients that occur with a wetter windshield, require powerful and therefore costly windshield wiper drives.

ADVANTAGES OF THE INVENTION

[0005] The wiper blade, in accordance with the invention for a windshield wiper, in particular for a windshield wiper of a motor vehicle, with the features in accordance with the pre-characterizing clause of Patent Claim 1, in which the wiper blade rubber lip is fabricated partially of polyethylene, has the advantage, on the other hand, that by using polyethylene as a material for the wiper blade rubber lip, low dry friction coefficients μ_(tr) can be achieved.

[0006] Under certain operating conditions, this leads to a lower development of noise as compared with the state of the art and namely even with a dry windshield.

[0007] Because of the dry friction coefficients of the wiper blade in accordance in the invention that are low as compared to the state of the art, wiper drives of smaller dimensions with corresponding reduced power can be used advantageously.

[0008] The wiper blade rubber lip can either be coated with polyethylene and/or contain polyethylene in volume.

[0009] According to a preferred embodiment, the polyethylene is PE-UHMW. PE-UHMW, i.e., polyethylene with an ultrahigh molecular weight, is especially suited to coat wiper blade rubber lips since it already has a low dry friction coefficient as a whole material. Thus, for example, a whole material specimen of PE-UHMW with a contact length of 8 mm and a load of 0.128 N on a rotating glass shaft, which is moving at 0.1 m/s, has a dry friction coefficient of μ_(tr) 0.21.

[0010] In the case of vulcanization of a rubber material, which is coated with PE-UHMW, the PE-UHMW combines adhesively with the rubber material through diffusion. If the PE-UHMW is applied to the rubber material as a powder, it sinters during vulcanization. PE-UHMW in particular adheres on a rubber material in such a way that the polyethylene/rubber material bond tears starting at a certain load in the bond.

[0011] Alternatively, the polyethylene of the wiper blade in accordance with the invention can be PE-HD, i.e., high-density polyethylene, or even PE-X, i.e., interlaced polyethylene. PE-X in particular is applied in molten form to a rubber material during the manufacture of the wiper blade in accordance with the invention and thermally secondarily cross-linked during vulcanization.

[0012] The invention also deals with a process to manufacture a wiper blade for a windshield wiper, which is comprised of a wiper blade rubber with a wiper blade rubber lip. With this process, the wiper blade rubber lip is manufactured by vulcanizing a rubber material together with polyethylene.

[0013] The rubber material can be manufactured on the basis of natural rubber. Using synthetic rubber materials as the base material for the wiper blade rubber lip is also conceivable, however.

[0014] In a preferred embodiment of the process in accordance with the invention, the vulcanization takes place under the conditions that are customary for vulcanizing a rubber.

[0015] It is preferred that the polyethylene be present in powder form as a primary material and, namely, with a grain size of approx. 0.1 μm to 30 μm.

[0016] In a preferred embodiment of the process according to the invention, the rubber material is coated with polyethylene before vulcanization. The vulcanization of the molded part coated with polyethylene can then take place in a mold. The vulcanized work piece made of the rubber material and the polyethylene can be demolded easily.

[0017] The coating of the rubber material with polyethylene that takes place before the joint vulcanization can occur in such a way that the rubber material put into the mold can be coated with a dispersion containing polyethylene particles, or that the rubber material can be dusted with polyethylene powder. A customary electrostatic powder coating process is particularly suited for applying a polyethylene powder. The unvulcanized rubber material is advantageously dusted all-over with PE powder. A partial is covering is possible, however.

[0018] However, the polyethylene can also be applied by means of a fluidized bed. In an advantageous embodiment, the rubber material in this case becomes hot and is extruded from an extrusion head in a tacky manner. The rubber material then makes its way through an opening into the lowly concentrated fluidized bed of very fine PE-UHMW powder with a grain size between 0.1 μm and 15 μm, and then leaves the fluidized bed through an opening, in order to then be blown on by clean purging air. As a result, the polyethylene particles that do not adhere to the rubber material are removed. The purging air also can in turn be used to operate the fluidized bed.

[0019] With another embodiment of the process according to the invention, unvulcanized rubber material is pressed into a mold in a hot press with a special steel tool, for example, at a temperature of 180° C. and a pressure of 70 bar for a duration of 10 seconds, then removed and cooled down with water. After drying, the partially vulcanized rubber molded part that was fabricated in this way is thinly dusted on both sides with PE-UHMW powder. Finally, the dusted molded part is vulcanized at a pressure of 70 bar, a temperature of 180° C. for a duration of 5 minutes in a mold corresponding to the rubber molded part.

[0020] However, the rubber material and the polyethylene can also be combined with one another in accordance with a co-extrusion process. In the case of co-extrusion, a polyethylene melt, polyethylene film, polyethylene monofilament or polyethylene cord is fed in this process at least in the area of the wiper blade rubber lip of the wiper blade rubber. Finally, the rubber material and the polyethylene adjacent to it are jointly vulcanized.

[0021] However, it is also possible to manufacture the wiper blade rubber with the wiper blade rubber lip in accordance with an injection molding process. In this case, a film, a monofilament or a cord of polyethylene is put into an injection mold before injection molding, or else the injection mold is coated with a dispersion or a powder of polyethylene.

[0022] If the polyethylene is supposed to be contained in volume in the wiper blade rubber lip, the wiper blade rubber lip is expediently manufactured of a mixture, which is comprised of the rubber material and the polyethylene.

[0023] According to an advantageous embodiment, the mixture contains between 1% and 50% polyethylene powder, in particular PE-UHMW powder.

[0024] Additional advantages and advantageous further developments of the subject of the invention are yielded from the description, the drawings and the patent claims.

DRAWINGS

[0025] Four exemplary embodiments of the wiper blade in accordance with the invention of a windshield wiper device of a motor vehicle are shown schematically simplified in the drawings and are explained in greater detail in the following description. The drawings show:

[0026]FIG. 1 A depiction of the principle of a wiper blade in cross-section.

[0027]FIG. 2 A cross-sectional depiction of a second embodiment of a wiper blade.

[0028]FIG. 3 A third embodiment of a wiper blade in cross-section.

[0029]FIG. 4 A fourth embodiment of a wiper blade.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0030]FIG. 1 depicts a wiper blade, which is composed of a wiper lip 2 featuring a wiper edge 5 made of rubber material, a head piece 3 made of rubber material (shown only partially in this case) and a so-called reversing bridge 4 made of rubber material, which is arranged between the head piece 3 and the wiper lip 2.

[0031] The wiper lip 2, the head piece 3 and the reversing bridge 4 are provided with a surface formed by a polyethylene layer 1, which for the sake of clarity is shown in FIG. 1 enlarged as compared to the wiper lip 2, the head piece 3 and the reversing bridge 4. The polyethylene layer 1 is composed primarily of PE-UHMW, i.e., of polyethylene with an ultrahigh molecular weight.

[0032] The wiper blade in accordance with FIG. 1 is manufactured in such a way that first partially vulcanized rubber material is pressed into a wiper blade mold in an extruder by means of a tool, then dusted with PE-UHMW powder and finally vulcanized. The conditions for vulcanization correspond to customary vulcanization conditions.

[0033] The resulting material quality of the wiper blade rubber lip is such that in the case of a measurement where the wiper blade 1 is adjacent to a rotating glass plate and the wiping speeds as well as the pressure conditions are like with a motor vehicle, dry friction coefficients μ_(tr) between 0.32 and 0.48 can be achieved.

[0034] The exemplary embodiment of a wiper blade depicted in FIG. 2 is comprised essentially of the same components as the wiper blade according to FIG. 1. However, the wiper blade according to FIG. 2 differs from the one according to FIG. 1 because of a so-called wiper edge 5, which is free of polyethylene.

[0035] The exemplary embodiment of the wiper blade depicted in FIG. 3 is also comprised essentially of the same components as the exemplary embodiment according to FIG. 1, but it differs from the latter, however, in that the wiper edge 5 embodied on the wiper lip 2, the reversing bridge 4 and the heard piece 3 are free of polyethylene and the wiper lip 2 is coated with polyethylene only on its lateral areas adjacent to the wiper edge 5, i.e., it is only partially coated with polyethylene.

[0036] The exemplary embodiment shown in FIG. 4 shows a wiper blade, which essentially is comprised of only a partially depicted head piece 3 made of rubber material, a reversing bridge 4 made of rubber material that attaches to the head piece 3 and a wiper lip 6 with a wiper edge 5. The wiper lip 6 is composed of a rubber material in which polyethylene in the form of PE-UHMW is embedded. The wiper lip 6 is manufactured of a primary material, which contains approx. 40% polyethylene.

[0037] The wiper blade rubber at hand is an extrusion part. Alternatively, the wiper blade rubber can be manufactured in a known manner also in accordance with an extrusion process or by compression molding. 

1. Wiper blade for a windshield wiper, in particular for a windshield wiper of a motor vehicle, with a wiper blade rubber, which features a wiper blade rubber lip (2, 6), characterized in that the wiper blade rubber lip (2, 6) is fabricated partially of polyethylene.
 2. Wiper blade according to claim 1, characterized in that the wiper blade rubber lip (2) is coated with polyethylene (1).
 3. Wiper blade according to claim 1 or 2, characterized in that a head piece (3) is attached to the wiper blade rubber lip (2) via a reversing bridge (4) and that the wiper blade rubber lip (2), the reversing bridge (4) and the head piece (3) are coated with polyethylene (1).
 4. Wiper blade according to one of claims 1 through 3, characterized in that the wiper blade rubber lip (2) is coated partially with polyethylene (1).
 5. Wiper blade according to one of claims 1 through 4, characterized in that the wiper blade rubber lip (6) contains polyethylene in volume.
 6. Wiper blade according to one of claims 1 through 5, characterized in that the polyethylene is a PE-UHMW.
 7. Wiper blade according to one of claims 1 through 5, characterized in that the polyethylene is a PE-HD.
 8. Wiper blade according to one of claims 1 through 5, characterized in that the polyethylene is a PE-X.
 9. Process to manufacture a wiper blade for a windshield wiper, which is comprised of a wiper blade rubber with a wiper blade rubber lip, characterized in that the wiper blade rubber lip is manufactured by vulcanizing a rubber material together with polyethylene.
 10. Process according to claim 9, characterized in that the polyethylene is in powder form as a primary material and has a grain size of less than 30 μm.
 11. Process according to claim 9 or 10, characterized in that the rubber material is coated with the polyethylene before vulcanization.
 12. Process according to claim 11, characterized in that the rubber material is coated with a dispersion containing polyethylene particles.
 13. Process according to claim 11, characterized in that the polyethylene is applied to the rubber material in accordance with an electrostatic powder coating process.
 14. Process according to claim 11, characterized in that the polyethylene is applied to the rubber material by means of a fluidized bed.
 15. Process according to claim 11, characterized in that the rubber material and the polyethylene are combined with one another in accordance with a co-extrusion process.
 16. Process according to one of the claims 11 through 15, characterized in that the rubber material coated polyethylene is exposed to purging air.
 17. Process according to claim 9 or 10, characterized in that the wiper blade rubber lip is manufactured of a mixture, which is comprised of the rubber material and the polyethylene.
 18. Process according to claim 17, characterized in that the mixture contains between 1% and 50% polyethylene powder. 